Multispectral remote sensing images are acquired from aircraft and satellites. To quantify ground surface characteristics, the measured spectral radiances must be converted into target reflectance. In these applications, accurate and consistent sensor calibration is essential. Out-Of-Band (“OOB”) response is defined as the ratio of integrated response outside the one percent of peak response points of a spectral band to the integrated response inside the one percent points. Several multispectral radiometric instruments are known to exhibit significant radiance contribution from OOB spectral response.
The typical scale of OOB spectral response is in the range of several percent, which can, for example, result in chlorophyll retrievals that are biased high for clear water by OOB response to short wavelengths. A methodology to dealing with the OOB response had been suggested and adopted for SeaWiFS calibration. These calibration methods adjust the measured radiances to correct for OOB response for ease of comparison to in situ measured multispectral radiances. The SeaWiFS correction scheme has been successfully applied to data products retrieved over Case 1 ocean waters. “Case 1” ocean waters are those for which the inherent optical properties are determined primarily by phytoplankton and co-varying chromophoric dissolved organic matter (“CDOM”) and detritus. However, the correction scheme is inherently not useable for SeaWiFS data product corrections over Case 2 turbid waters or over land.
The first VIIRS instrument, Flight Unit 1 (“FU1”), now flying on the NPP satellite platform, has known performance issues. Seven channels located between 0.4 and 0.9 μm in the VisNIR focal plane have problems related to OOB responses, i.e., small amounts of radiance far away from the center of a given channel that pass through the filter and reach the detector. The newly launched VIIRS instrument requires developing highly accurate operational calibration procedures and algorithms to process VIIRS data.